1. Field of the Invention
The present invention relates to a fluid transmitting system such as a torque converter and a fluid coupling, used in a power transmitting system for a vehicle or an industrial machine, and particularly to a fluid transmitting system with a lock-up clutch, comprising a pump impeller, a turbine runner which defines a circulation circuit between the turbine runner and the pump impeller, a side cover which is connected to the pump impeller and which defines a clutch chamber between the side cover and an outer side of the turbine runner to communicate with an outer peripheral portion of the circulation circuit, and a lock-up clutch disposed in the clutch chamber and capable of coupling the side cover and the turbine runner directly to each other, the lock-up clutch being comprised of a clutch piston axially movably connected to the turbine runner to divide the clutch chamber into an inner oil chamber section on the side of the turbine runner and an outer oil chamber section on the side of the side cover, a lock-up control means adapted to generate a difference in pressure between the inner oil chamber section and the outer oil chamber section to advance and retract the clutch piston to and from an inner side of the side cover, a friction engaging means adapted to bring the clutch piston and the side cover into friction engagement with each other when the clutch piston is pushed against the inner side of the side cover, and a resilient member disposed between the clutch piston and the turbine runner to bias the clutch piston toward the inner side of the side cover.
2. Description of the Related Art
Such fluid transmitting system with the lock-up clutch is already known, as disclosed in, for example, Japanese Patent Application Laid-open No. 55-54758.
In such a fluid transmitting system with the lock-up clutch, the resilient member for biasing the clutch piston toward the inner side of the side cover is arranged so that when the lock-up control means is operated to bring the lock-up clutch into engaged state, the delay of the operation of the clutch piston is eliminated, leading to an enhancement in responsiveness to the engagement of the lock-up clutch.
In the conventional fluid transmitting system with the lock-up clutch, one end of the resilient member is secured to a piston hub of the clutch piston and hence, there is a possibility that the deformation attitude of the resilient member is restrained by the piston hub and as a result, the resilient member generates a needless stress and cannot exhibit an intrinsic spring characteristic, and further the durability of the resilient member is deteriorated.